Photocurable compositions for stereolithography, method of forming the compositions, stereolithography methods using the compositions, polymer components formed by the stereolithography methods, and a device including the polymer components

ABSTRACT

A photocurable composition for stereolithographic three-dimensional printing, wherein the photocurable composition comprises a photoreactive oligomer component comprising a hydrophobic oligomer comprising a photoreactive end group, a photoreactive monomer component comprising a photoreactive monomer having a photoreactive end group, and a photoinitiation composition comprising a photoinitiator; the photocurable composition has a viscosity of 250 to 10,000 centipoise at 22° C., determined using a Brookfield viscometer; and the photocured composition has a dielectric loss of less than 0.010, preferably less than 0.008, more preferably less than 0.006, most preferably less than 0.004, each determined by split-post dielectric resonator testing at 10 gigahertz at 23° C.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 62/854,387, filed May 30, 2019, the content of which isincorporated herein by reference in its entirety.

BACKGROUND

This disclosure is directed to a photocurable composition forstereolithography, a method of forming the photocurable composition, astereolithographic method using the composition, a component formed bythe stereolithographic method, and a device including the component.

Additive manufacturing (AM), which includes 3-dimensional (3D) printingand solid free-form fabrication, allows the production ofthree-dimensional objects of virtually any shape from a digital model.Generally, this is achieved by creating a digital blueprint of a desiredstructure with computer-aided design (CAD) modeling software and thenslicing that virtual blueprint into digital cross-sections. Thesecross-sections are formed or deposited in a sequential layering processto create the 3D structure.

One application of AM is the formation of electronic components for usein high frequency wireless transmission such as antenna elements,radomes, and lenses. Stereolithography apparatus (SLA) printing is apreferred method of AM for forming these components because of the highprint speeds and high-resolution capability. A wide variety of materialshave been developed for use in SLA printing, but these materials havehigh dielectric loss factors (Df) of greater than 0.01 when measured athigh frequency such as 10 gigahertz. Therefore, there remains a need inthe art for improved materials to provide printed structures having Dfof less than 0.01 at 10 gigahertz.

BRIEF SUMMARY

A photocurable composition for stereolithographic three-dimensionalprinting is disclosed, wherein the photocurable composition comprises aphotoreactive oligomer component comprising a hydrophobic oligomercomprising photoreactive end groups, a photoreactive monomer component,and a photoinitiation composition comprising a photoinitiator; thephotocurable composition has a viscosity of 250 to 10,000 centipoise at22° C., determined using a Brookfield viscometer; and the photocuredcomposition has a dielectric loss of less than 0.010, preferably lessthan 0.008, more preferably less than 0.006, and most preferably lessthan 0.004, each determined by split-post dielectric resonator testingat 10 gigahertz (GHz).

Also disclosed is a method for the manufacture of a photocuredthree-dimensional structure using the photocurable composition.

The photocured three-dimensional structures made by the above method arealso disclosed.

In another aspect, an electronic device comprises photocuredthree-dimensional structure.

The above described and other features are exemplified by the followingfigures, detailed description, examples, and claims.

DETAILED DESCRIPTION

Stereolithography is a specialized 3D printing method also referred toin the art as optical fabrication, photosolidification, and resinprinting. Any of the foregoing methods can be used herein and arereferred to collectively as “SLA” methods. In these methods, successivethin layers of a liquid resin are selectively photocured using a lightsource. The light source can be located at either the top or the bottomof the stack of layers. Photocurable compositions are available for usein SLA printing, but there remains a need in the art for compositionsthat provide photocured components having very low dielectric loss andare suitable for use in electronic devices operating at high frequency.As is known in the art, developing a photocurable composition that canbe used in SLA printing to provide a desired set of properties requiresa careful balancing of properties needed for efficient SLA manufactureand the desired properties in the photocured component. Efficient SLAmanufacture relies on photocurable compositions having a narrow range ofsuitable viscosity and photocure time. This is particularly difficult toachieve for advanced materials designed for very low loss electroniccomponents. Such components are needed for higher operating frequenciessuch as in 5G networks, for example. Suitable materials have a narrowwindow of desirable properties that are difficult to achieve using anymanufacturing method, including most notably very low loss (e.g., a Dfless than 0.01 at 10 gigahertz (GHz)). Achieving SLA-printablecompositions for very low loss electronic components is particularlydifficult because any single change to attain a desired property such aslow loss can adversely affect printability of the photocurablecomposition, and any change to improve printability of the compositioncan adversely affect the desired properties of the photocured polymer.

The inventors hereof have discovered photocurable compositions thatpermit efficient manufacture of three-dimensional polymeric structuresusing SLA manufacturing methods, and that provide photocured polymercompositions having very low loss, in particular having a dissipationfactor (Df) of less than 0.01 when measured at 10 GHz. The compositionsare specific formulations that can further provide three-dimensionalpolymer articles with other desired properties for use in electroniccomponents, especially those operating at high frequency.

The SLA printable compositions are photocurable and include a specificphotoreactive oligomer component and photoreactive monomer component,together with a photoinitiator system and an optional ceramic filler.

The photoreactive oligomer component includes a hydrophobic, nonpolar oramphipathic oligomer comprising a reactive group that can participate ina photocuring reaction, i.e., a free-radically photopolymerizable group.The oligomeric backbones of the photoreactive oligomers are preferablynonpolar or amphipathic, and hydrophobic, and typically comprisehydrocarbon repeat units or aliphatic ester repeat units. As is known inthe art, hydrophobicity is correlated with materials that are lesslikely to accept or donate hydrogen bonds to water. For example, apreferred hydrophobic oligomer backbone is a polybutadiene, whichcomprises a non-polar, hydrophobic segment. Another hydrophobic oligomerbackbone is a poly(C₄₋₆ alkylene) ester backbone. Additional functionalgroups can be present in the backbone, as linkers, for example carbamateester (urethane), ether, ester, amide, ketone, and the like, which canrender some degree of amphipathic character to the backbone.

At least one photoreactive group is present in the photoreactiveoligomer, preferable as an end (i.e., terminal) group. More preferably,more than one photoreactive group is present as an end group, i.e., atleast two photoreactive terminal groups are present. Such groups caninclude alkenyl groups such as vinyl and allyl, as well as(meth)acryloyl end groups such as acrylate and methacrylate.Free-radically photopolymerizable groups can also include terminalalkynyl groups such as terminal propargyl (2-propynyl). Preferredphotoreactive end groups are (meth)acrylates, which as used hereinincludes both acrylate and methacrylate groups. Even more preferred aremethacrylate end groups.

The photoreactive oligomers are commercially available or can bemanufactured by methods known in the art from precursors that includereactive functional groups such as hydroxyl, carboxylic acid,isocyanate. For example, a (meth)acrylate-functional oligomericpolyester or a (meth)acrylate-functional oligomeric polyurethane can bederived from the following categorized precursors (Category A throughCategory G):

Category A:

-   -   Aliphatic polybasic carboxylic acids such as succinic acid,        adipic acid, azelaic acid, sebacic acid,        1,2,4-butanetricarboxylic acid and 1,2,3,4-butanetetracarboxylic        acid.    -   Cycloaliphatic polybasic carboxylic acids such as 1,2-, 1,3-,        1,4-cyclohexanedicarboxylic acid, hexahydrophthalic acid and        hexahydroterephthalic acid.    -   Aromatic polybasic carboxylic acids such as phthalic acid,        isophthalic acid, terephthalic acid, trimellitic acid,        pyromellitic acid, naphthalene dicarboxylic acid,        4,4-diphenyldicarboxylic acid, and        diphenylmethane-4,4′-dicarboxylic acid.    -   Anhydrides such as hexahydrotrimellitic acid and methyl        hexahydrophthalic acid.    -   Alkenyl polybasic carboxylic acids such as maleic acid, fumaric        acid, itaconic acid, HET acid, tetrahydrophthalic acid.

Category B:

-   -   Aliphatic polyhydric alcohols such as ethylene glycol, propylene        glycol, 2,3-dimethyltrimethylene glycol, 1,2-, 1,3-,        1,4-butanediol, 2,3-butanediol, 3-methyl-1,2-butanediol, 1,2-,        1,4-, 1,5-pentanediol, 2,4-pentanediol,        3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol,        neopentyl glycol, 1,4-, 1,5-, 1,6-hexanediol, 2,5-hexanediol,        1,2,6-hexanetriol, trimethylolpropane, trimethylolethane,        pentaerythritol and glycerol.    -   Polyether polyhydric alcohols such as diethylene glycol,        triethylene glycol, tetraethylene glycol, dipropylene glycol,        dipentaerythritol, diglycerol, spiroglycol and triglycerol.    -   Cycloaliphatic polyhydric alcohols such as tricyclodecane        dimethanol, 1,3-, 1,4-cyclohexane dimethanol, hydrogenated        bisphenol A and hydrogenated bisphenol F.    -   Aromatic polyhydric alcohols such as        bis(hydroxyethyl)terephthalate.    -   Alkenyl polyhydric alcohols such as        hydroxyl-terminated-polybutadiene.

Category C

-   -   Polyester polyols derived from the ring opening polymerization        of lactones such as β-propiolactone, γ-butyrolactone,        α-methyl-γ-butyrolactone, δ-valerolactone, ε-caprolactone,        α-chloro-ε-caprolactone, γ-methyl-ε-caprolactone,        ε-heptalactone, ε-decalactone, ω-pentadecalactone and        7-isopropyl-4-methyloxepan-2-one.    -   Alkenyl polyester polyols derived from the ring opening        polymerization of lactones such as α-methylene-γ-butyrolactone,        4-isopropenyl-7-methyloxepan-2-one, and        α-propargyl-ε-caprolactone.

Category D

-   -   Aliphatic diisocyanates such as hexamethylene diisocyanate        (HMDI), trimethylhexamethylene diisocyanate.    -   Cycloaliphatic diisocyanates such as isophorone diisocyanate        (IPDI), cyclohexane-1,4-diisocyanate and        4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI).    -   Aromatic diisocyanates such as 2,4-tolylene diisocyanate        (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI),        4,4′-diphenylmethane diisocyanate, 1,4-phenylene diisocyanate,        1,5-naphthalene diisocyanate, xylylene diisocyanate, and        tetramethylxylylene diisocyanate.

Category E

-   -   Isocyanates containing an α,β-unsaturated ketone such as        (meth)acryloylisocyanate and 2-isocyanatoethyl (meth)acrylate.    -   Isocyanates containing photoreactive alkenes such as        m-,p-isopropenyl-α,α′-dimethylbenzyl isocyanate and vinyl        isocyanate.

Category F

-   -   Hydroxy-containing α,β-unsaturated ketone monomers such as        2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,        4-hydroxybutyl (meth)acrylate, polyethylene glycol        mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl        (meth)acrylate.

Category G

-   -   α,β-unsaturated carboxylic acid monomers such as (meth)acrylic        acid and β-carboxyethyl (meth)acrylate.

In particular, at least one member from at least two differentcategories are reacted. Photoreactive (meth)acrylate-functionaloligomeric polyesters can be prepared by reacting the abovecategory-specific materials to produce a variety of structuralsequences. For example, reaction of a component from category F and Gcan be used to produce a polyester of sequence FG. Other sequences thatcan be produced include FCG, FAF, GBAF, GBCG, FCACF and GBABG.

Photoreactive (meth)acrylate functional oligomeric polyurethanes canalso be prepared by reacting the above category specific materials toproduce the following structural sequences, for example: FE, EBE, FCE,FDF, GBE, FDBDF, FCDCF and EBABE.

The number average molecular weight of the photoreactive, hydrophobicoligomer can be 250 to 10,000 grams per mole (g/mol), for example 500 to5,000 g/mol, 700 to 5,000 g/mol ole, or 1,000 to 4,000 g/mol.

A preferred photoreactive oligomer is a (meth)acrylate-functionaloligomeric polyester containing an aliphatic urethane linking group, andproduced by reaction of caprolactone, hydroxyethyl acrylate, acrylicacid, and 4,4′-dicyclohexyl diisocyanate. Other diisocyanates asdescribed below can be used. Preferred oligomers of this type arecommercially available from Sartomer (Arkema Group), for example underthe trade name CN 9014 NS.

Another preferred photoreactive oligomer is a urethane(meth)acrylate-derivatized polybutadiene oligomer. Such oligomers can beobtained by derivatization of a hydroxyl-terminated polybutadiene with a(C₁₋₆-alkyl)(meth)acrylate-functionalized isocyanate.

The hydroxyl-terminated polybutadiene can have a structure of formula(1)

wherein x, y, and z are molar ratios of each unit, can vary from 0 to 1,and x+y+z=1.

The (C₁₋₆-alkyl)(meth)acrylate-functionalized isocyanate can be offormula (2)

wherein R¹ is a C₃₋₃₆ organic group and R² is hydrogen or methyl.Examples wherein R¹ is ethyl include acryloyloxyethyl isocyanate andmethacryloyloxyethyl isocyanate. In an aspect R¹ is a substituted orunsubstituted C₆₋₃₆ aromatic group, preferably a substituted C₇₋₁₅aromatic group. Compounds of formula (2) can be derived fromdiisocyanates. Examples of such diisocyanates include 2,4-toluenediisocyanate, 2,6-toluene diisocyanate, 4,4′-diphenyl methanediisocyanate (MDI), 4,4′-dicyclohexyl diisocyanate, m- and p-tetramethylxylylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethyl cyclohexylisocyanate (isophorone diisocyanate), hexamethylene diisocyanate (HMDI),1,5-naphthylene diisocyanate, dianisidine diisocyanate,di-(2-isocyanatoethyl)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate,2,2,4- and 2,4,4-trimethylene hexamethylene diisocyanate. Compounds offormula (2) can also be derived from the reaction of diisocyanates with(meth)acrylic hydroxy compounds such as 2-hydroxyethyl acrylate and2-hydroxy ethyl methacrylate. In an aspect the diisocyanate may compriseisophorone diisocyanate, methylene-bis-phenyl diisocyanate, toluenediisocyanate, hexamethylene diisocyanate, m-tetramethylxylylenediisocyanate, or a combination thereof. Further in formula (2), R² ispreferably hydrogen.

In an aspect the urethane (meth)acrylate-derivatized polybutadieneoligomer has a structure of formula (1)

wherein n is 10 to 1000 and is selected to provide a number averagemolecular weight within the above range. Also, a urethanemethacrylate-derivatized polybutadiene oligomer of formula (2) can beused,

wherein n is 10 to 1000 and is selected to provide a number averagemolecular weight within the above range. In formulas 1 and 2, each n canbe independently selected. A combination of different urethane(meth)acrylate-derivatized polybutadienes can be used.

A preferred oligomer is a urethane (meth)acrylate-derivatizedpolybutadiene oligomer having a specific molecular weight range. Thenumber average molecular weight is 500 to 5,000 g/mol, 700 to 5,000g/mol, or 1,000 to 4,000 g/mol. Suitable urethanemethacrylate-derivatized polybutadienes are commercially available, forexample from Dymax, Sartomer, or Nippon Soda.

The photocurable compositions further comprise a photoreactive monomercomponent to adjust the viscosity of the overall composition and toprovide crosslinking with the photoreactive oligomer. The photoreactivemonomers can include one or more free-radically photopolymerizablegroups such as (meth)acrylate groups. Preferably functional groups otherthan alkenyl, alkynyl, or (meth)acryl groups are not present, such ascarboxylic acid, hydroxyl, sulfhydryl, and amino groups. In a surprisingaspect, it has been found that methacrylate groups are preferred, asmethacrylate-terminated compounds provide an improved combination ofproperties (see, e.g., Table 1). In particular, it has been found thatthe best results are obtained when the photocurable components of thecomposition (the oligomer and monomer components) comprise 20 wt % orless of monomers containing terminal acrylate groups (see, e.g.,Example, 4, Table 6).

Suitable photoreactive monomers can be mono-, di-, tri-, tetra-, orpenta-functional, having 1, 2, 3, 4, or 5 unsaturated groupsrespectively, preferably 1, 2, or 3 (meth)acrylate groups. A combinationof different monomers can be used, for example a monofunctional monomerand a difunctional monomer. Exemplary photoreactive monomers can includearomatic groups, or cyclic or acyclic aliphatic groups. Exemplaryaromatic monomers include benzyl(meth)acrylate, naphthyl(meth)acrylate,phenoxyethyl(meth)acrylate, and phenyl(meth)acrylate. In an aspect, noaromatic (meth)acrylates are present in the photocurable compositions.

Preferably the photoreactive monomers are cyclic or acyclic aliphaticmonomers to provide low Df. Exemplary cyclic aliphatic (meth)acrylatemonomers include cyclopentyl(meth)acrylate, cyclohexyl(meth)acrylate,cyclohexyldi(meth)acrylate and isobornyl(meth)acrylate.

Exemplary acyclic aliphatic (meth)acrylate monomers include (C₁₋₁₈alkyl) (meth)acrylates such as methyl methacrylate, ethyl methacrylate,iso-butyl(meth)acrylate, tert-butyl(meth)acrylate,iso-decyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate,ethoxyethoxyethyl(meth)acrylate (ethyl carbitol (meth)acrylate)), 1,2-,1,3-, and 1,4-butanediol di(meth)acrylate, 1,2-, 1,3-, 1,4-, 1,5- and1,6-hexanediol di(meth)acrylate and combinations thereof, ethyleneglycoldi(meth)acrylate, propylene glycol di(meth)acrylate, diethyleneglycoldi(meth)acrylate, triethyleneglycol di(meth)acrylate, polyethyleneglycol di(meth)acrylate, dipropyleneglycol di(meth)acrylate,triethyleneglycol di(meth)acrylate, glycerol tri(meth)acrylate, 1,2- and1,3-propanediol di(meth)acrylate, ethoxylated trimethylolpropanetri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, or tris (2-hydroxyethyl) isocyanuratetri(meth)acrylate.

Although (meth)acrylates are preferred, other alkenyl photoreactivemonomers can be present, such as triallyl isocyanurate,allyl(meth)acrylate, pentaerythritol diallyl ether, pentaerythritoltriallyl ether, pentaerythritol tetraallyl ether, diallyl ether,tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane, styrene,alpha-methyl styrene, divinylbenzene, divinyltoluene, diallyl phthalate,divinyl xylene, trivinyl benzene, or divinyl ether.

Although (meth)acrylates are preferred, other alkynyl photoreactivemonomers can be present, such as dipropargyl, phenyl propargyl ether,benzyl propargyl ether, propargyl benzoate, propargyl ether, ortripropargyl cyanurate.

The photoreactive monomers used can possess combinations of(meth)acryloyl, alkenyl, and alkynyl functional groups such as vinyl(meth)acrylate, allyl (meth)acrylate, propargyl (meth)acrylate, vinylacetylene, allyl vinyl acetylene, N,N-methylene bisacrylamide,N,N-methylenebismethacrylamide, or allyl vinyl ether.

The inventors hereof have found that certain photoreactive monomers areespecially suitable for use in the photocurable monomer components,including isobornyl (meth)acrylate, ethylene glycol dimethacrylate,1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate,2-ethylhexyl (meth)acrylate, hydroxypropyl methacrylate, 1,3-butanedioldimethacrylate, or a combination thereof. The isobornyl (meth)acrylatecan be isobornyl methacrylate or isobornyl acrylate. A combination canbe used. The 1,6-hexanediol di(meth)acrylate can be 1,6-hexanedioldimethacrylate or 1,6-hexanediol diacrylate. A combination can be used.As illustrated in the examples, use of these monomers provides thedesired degree of cure (crosslinking and polymerization) to achieve a Dfof less than 0.01 when measured at 10 GHz, and to prevent the migrationof lower molecular weight components from the photocured polymer.

Generally, the photocurable compositions can include 25 to 85 weightpercent (wt %) of the photoreactive oligomer component; 25 to 65 wt % ofthe photoreactive monomer component; and 0.1 to 15 wt %, preferably 0.1to 5 wt %, of the photoinitiation composition, wherein each weightpercent is based on the total weight of the photoreactive oligomercomponent, the photoreactive monomer component, and the photoinitiationcomposition, and totals 100 weight percent. In another aspect, thephotocurable compositions can include 35 to 85 wt % of the photoreactiveoligomer component; 15 to 65 wt % of the photoreactive monomercomponent; and 0.1 to 15 weight, preferably 0.1 to 5 wt %, of thephotoinitiation composition, wherein each weight percent is based on thetotal weight of the photoreactive oligomer component, the photoreactivemonomer component, and the photoinitiation composition, and totals 100weight percent.

It has been surprisingly found that an advantageous combination ofviscosity, cure speed, degree-of-cure, and physical properties in thephotocured components can be obtained using specific amounts of eachmonomer together with the addition of a particulate ceramic filler,where the amounts vary for each monomer and ceramic filler. Inparticular, use of the specific components in specific amounts canprovide a viscosity that has sufficient flow and self-levelingcharacteristics, together with fast cure for use in SLA methods, as wellas low loss and other properties such as low moisture absorption in thephotocured composition. Use of a particulate ceramic filler can be usedto adjust both viscosity and dielectric constant. It can especiallyenable attainment of a wider range of dielectric constant. Finally, useof filler can enable use of less high cost components lowering overallcost of the composition.

Accordingly, the photocurable composition can optionally comprise aparticulate ceramic filler to adjust the properties of the photocuredcomponent, in particular the dielectric constant. In a preferredembodiment the particulate filler is present, at least in part to adjustthe dielectric constant of the photocured component to the desiredrange. The particulate filler can comprise silica, alumina, calciumtitanate (CaTiO₃), strontium titanate (SrTiO₃), barium titanate(BaTiO₃), barium nonatitanate (Ba₂Ti₉O₂₀), boron nitride, aluminumnitride, or a combination thereof.

Using higher dielectric constant (Dk) fillers can enable the manufactureof porous structures, and still achieve the desired Dk. Preferred highdielectric constant fillers include silica, alumina, strontium titanate,barium nonatitanate, or a combination thereof. In some applications,more air is desirably incorporated into the porous structure. In thesestructures a particulate filler having a Dk of 5 or greater is desired,for example alumina, strontium titanate, barium titanate, bariumnonatitanate, or a combination thereof.

Other fillers can be used, provided that the filler does notsignificantly adversely affect the cure or desired Dk of thephotocurable composition. For example, to avoid significantly adverselyaffecting the cure of the photocurable composition, opaque fillers suchas many grades of titanium dioxide (titania) are minimized, and arepreferably excluded. To the extent that a filler such as a nanosizedtitania does not significantly adversely affect the length of cure orthe degree of cure, the filler can be present. To further avoidsignificantly adversely affecting the cure of the photocurablecomposition, the particulate filler can have a refractive index that iswithin a factor of two, for example, within a factor of 1.5, or within1.25, or within 1 of a refractive index of the photocured composition atthe wavelength of curing.

When present, the particulate filler is used in an amount of 5 to 60volume percent (vol %) of the photocurable composition, or 10 to 50 vol%, or 10 to 40 vol %, or 10 to 30 vol %, each based on the total volumeof the photocurable composition, including the particulate filler. Theparticle size of the filler is selected to provide both adequate flow ofthe photocured composition, as well as the desired electrical andmechanical properties. For example, the filler can have a medianparticle size of less than 25 micrometers, or less than 15 micrometers.

The particulate filler can be coated with a dispersant to improve thedispersion of the filler in the photocurable composition. The dispersantcan comprise an alkyl silane coating, an alkenyl silane coating, analkynyl silane coating, a (meth)acryloyl silane coating, an amino silanecoating, a chlorinated silane coating, a fluorinated alkyl silanecoating, a zirconate coating, a titanate coating, or a combinationthereof. The coating agent can comprise phenyltrimethoxysilane,p-chloromethylphenyltrimethoxy silane, aminoethylaminotrimethoxy silane,aminoethylaminopropyltrimethoxy silane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxy silane, allyltrimethoxy silane,vinyltriethoxy silane, o-(propargyloxy)-n-(triethoxy-silylpropyl)urethane, phenyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane,(tridecafluoro-1,1,2,2-tetrahydrodecyl)-1-triethoxysilane,neopentyl(diallyl)oxytri(dioctyl)pyrophosphate zirconate,neopentyl(diallyl)oxytri(N-ethylenediamino)ethyl zirconate, oleyltitanate, or a combination thereof. In as aspect the dispersant is asilane coating such as phenyltrimethoxysilane or a titanate coating suchas oleyl titanate.

The particulate filler can be pretreated with the coating agent prior toforming the composition, or the coating agent can be added to thecomposition. The coating can be present in an amount of 0.1 to 2.0 wt %,or 0.3 to 1.2 wt %, based on the total weight of the particulate filler.

The photocurable composition further comprises a photoinitiationcomposition, which comprises a free radical photoinitiator, a compoundthat produces free radicals upon exposure to radiation such asultraviolet and/or visible radiation, in an amount sufficient toinitiate a polymerization reaction. The free-radical photoinitiator canbe a single compound, a mixture of two or more active compounds, or acombination of two or more different compounds (such as co-initiators).

In an aspect, the free radical photoinitiator is preferably anultraviolet light photoinitiator. Such photoinitiators includeacetophenones, benzophenones, benzoin ethers, thioxanthones,thioxanthone-fluorenes, coumarin, ketocoumarin, camphorquinone,anthraquinones, benzoyl phosphorus compounds, acridines, and triazenes.Examples include 2,2′-diethoxyacetophenone, 2,2′-dibutoxy acetophenone,2,2′-dimethoxy-α-phenyl acetophenone, 4-chloroacetophenone,2-hydroxy-2-methyl propiophenone, benzophenone,4,4′-dichlorobenzophenone, 4,4′-(diethylamino) benzophenone,3,3′-dimethyl-2-methoxy-benzophenone, 2,2′-dichloro-4-phenoxyacetophenone, 2-methyl-1-(4-(methylthio) phenyl)-2-morpholino-1-one,benzoyl benzoic acid, benzoyl benzoic acid methyl, 4-phenylbenzophenone, anthraquinone, iso-butyl benzoin ether, mixtures of butylisomers of benzoin butyl ether, benzoin, benzoin methyl ether, benzoinethyl ether, benzoin isopropyl ether, thioxanthone, 2-methylthioxanthone, isopropyl thioxanthone, 2,4-diethyl thioxanthone,2,4-diisopropyl thioxanthone, 9-phenyl acridine,phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide,diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide,2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-(3′,4′-dimethoxy-styryl)-4,6-bis (trichloromethyl)-s-triazine,2-(4′-methoxynaphthyl)-4,6-bis(trichloromethyl)-s-triazine, and2-(p-methoxy methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine. Theultraviolet light photoinitiator can be present in the photocurablecomposition in an amount of 0.01 to 15 wt %, or 0.2 to 10 wt %, whereineach weight percent is based on the total weight of the photoreactiveoligomer component, the photoreactive monomer component, and thephotoinitiator composition, and totals 100 weight percent.

The photoinitiation composition can further optionally comprise anultraviolet light-absorbing agent. The ultraviolet light-absorbing agentcan include a hydroxy benzophenone, such as 2,4-dihydroxy benzophenone,2,3,4-trihydroxy benzophenone, 2,2′-dihydroxy-4-methoxy benzophenone,2-hydroxy-4-methoxy benzophenone, or others. A combination thereof canbe used. The ultraviolet light-absorbing agent is present in an amountof 0.1 to 10 wt %, 0.1 to 5 wt %, or 0.3 to 3 wt %, wherein each weightpercent is based on the total weight of the photoreactive oligomercomponent, the photoreactive monomer component, and the photoinitiatorcomposition, and totals 100 weight percent.

The photoinitiation composition optionally still further comprises ascintillating agent. The scintillating agents can absorb high-energyinvisible radiant energy and emit, in response to excitation by theabsorbed energy, radiant energy of a lower level and longer wavelengththan the exciting energy but still of a shorter wavelength and higherenergy level than visible light. The scintillating agent can comprise apolycyclic aromatic compound. The scintillating agent can include2,5-diphenyloxazole, 1,4-bis-2-(5-phenyloxazolyl)-benzene), terphenyl,1,1,4,4-tetraphenylbutadiene2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene, or a combinationthereof. In another example, the scintillating agent can include alanthanide chelate, such as a tris complex of 2,6-pyridine dicarboxylicacid (dipicolinic acid, DPA), e.g., Li₃[Eu(DPA)₃]. Lanthanides that canbe used in the chelate include europium (Eu), samarium (Sm), dysprosium(Dy), terbium (Tb), or a combination thereof. The scintillating agentcan be a spin orbit coupling enhanced scintillating material, such asiridium-tris[2-(4-tosyl)pyridinato-NC²], or a pyrazolate-bridgedcyclometalated platinum(II) complex. A combination thereof can be used.The scintillating agent can be present in an amount of 0.01 to 2 wt %,0.05 to 1 wt %, or 0.1 to 1 wt %, wherein each weight percent is basedon the total weight of the photoreactive oligomer component, thephotoreactive monomer component, and the photoinitiator composition, andtotals 100 weight percent.

The photocurable composition can further comprise an additivecomposition, wherein the additive composition can comprise a flameretardant, a heat stabilizer, an antioxidant, a plasticizer, apolymerization inhibitor, an ultraviolet light stabilizer, or aviscosity modifier. A combination comprising at least one of theforegoing can be used.

The heat stabilizer or antioxidant can be a phosphite such as2-ethylhexyl diphenyl phosphite, diphenyl isodecyl phosphite,tri-isodecyl phosphite, distyryl pentaerythritol diphosphite,tris(2,4-di-tert-butylphenyl) phosphite, or bis(2,4-di-tetra-t-butylphenyl) pentaerythritol diphosphite; a thiopropionate or propionate such as dilauryl thiodipropionate, tetrakis[methylene-3-(3,5-di-tetra-butyl-4-hydroxyphenyl) propionate],isotridecyl-3-(3,5-di-tetra-butyl-4-hydroxyphenyl) propionate,isooctyl-3-(3,5-di-tetra-butyl-4-hydroxyphenyl) propionate,thiodiethylene bis[3-(3,5-di-tetra-tert-butyl-4-hydroxyphenyl)propionate, hexamethylene bis [3-(3,5-di-tetra-butyl-4-hydroxyphenyl)propionate]; a hindered aryl compound such as 4,4′ thiobis(6-tetra-butyl-m-cresol), 4,6-bis (octyl thiomethyl)-o-cresol,1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene,tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate,octadecyl-3-(3,5di-tert-butyl-4-hydroxyphenyl) propionate, triethyleneglycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, or2,2-methylenebis(4 methyl-6-(1-methylcyclohexyl)-phenol); a triazolesuch as 2-(2′-hydroxy-5′-methylphenyl benzotriazole,2-(2′-hydroxy-3′,5′-di-tetra-butyl-phenyl) benzotriazole,2-(2′-hydroxy-3′,5′-di-tetra-butyl-phenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-3′,5′-di-tetra-amylphenyl) benzotriazole,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenol,2-[2-hydroxy-3,5-di (1,1-dimethylbenzyl) phenyl]-2H-benzotriazole, orbis[2-hydroxy-5-tetrahydro-octyl 3-(benzotriazol-2-yl) phenyl] methane;a benzoate such as hexadecyl 3,5-di-tetra-butyl-4-hydroxybenzoate; atriazine such as 2-[4-[(2-hydroxy-3-dodecyl-oxy-propyl)oxy]-2hydroxyphenyl]-4,6-bis (2,4-dimethylphenyl)-1,3,5-triazine,2-[4-(4,6-bis-biphenyl-4-yl-[1,3,5] triazin-2-yl)-3-hydroxy-phenoxy]propionic acid 6-methyl-heptyl ester, or2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dimethylphenyl)-1,3,5-triazine,and the like. A combination of different compounds can be used.

In some aspect the photocurable resin composition further comprises athermally curable component and a thermal cure initiator to initiatethermal cure. Inclusion of a thermally curable component allowsmulti-stage curing of the polymer structure. Examples of additionalthermally curable compounds that optionally can be used in addition tothe photocurable oligomers and monomers can include1,3-dicyanatobenzene, 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene,1,3-dicyanatonaphthalene, 1,3,6-tricyanatoaphthalene,2,2′-dicyanatobiphenyl, bis(4-cyanatophenyl) methane,4-chloro-1,3-dicyanatobenzene, cyanated novolacs produced by reacting anovolac with cyanogen halide, and cyanated bisphenol polycarbonateoligomers produced by reacting a bisphenol polycarbonate oligomer withcyanogen halide. A combination of two or more thermally curablecompounds can be used. When present, the thermally curable componentscan be used in an amount of 5 to 85 wt %, 10 to 85 wt %, or 10 to 75 wt%, or 30 to 65 wt %, wherein each weight percent is based on the totalweight of the photocurable composition, the photoreactive oligomercomponent, the photoreactive monomer component, the photoinitiatorcomposition, the thermally curable components, and the thermal cureinitiator, and totals 100 weight percent.

Examples of thermal cure initiators include peroxides, certainnucleophilic catalysts, or certain metal coordination catalysts as isknown in the art. When present, the thermal cure initiator can be usedin an amount of 0.01 to 2 wt %, 0.05 to 1 wt %, or 0.1 to 1 wt %,wherein each weight percent is based on the total weight of thephotocurable composition, photoreactive oligomer component, thephotoreactive monomer component, the photoinitiator composition, thethermally curable components, and the thermal cure initiator, and totals100 weight percent.

As stated above, the photocurable compositions provide photocuredpolymer materials having a desirable combination of electrical andmechanical properties.

Dielectric loss (Df, also referred to as the dissipation factor or theloss tangent of a material) quantifies a dielectric material's inherentdissipation of electromagnetic energy. The photocured polymer materialscan have a dielectric loss factor of less than 0.01, or less than 0.008,or less than 0.006, or less than 0.004 each measured at a frequency of10 GHz. For example, the photocured polymer components can have adielectric loss factor of 0.0001 to 0.01, or 0.0001 to 0.008, or 0.0001to 0.006, or 0.0001 to 0.004, each measured at a frequency of 10 GHz.

Relative permittivity (Dk, also referred to as the dielectric constantof a material) is the measure of resistance that is encountered whenforming an electric field in a medium relative to that of a vacuum. Apermittivity of the photocured composition can be at least 2, or atleast 2.1. The permittivity of the photocured composition can be lessthan 18, or less than 14, or less than 10. For example, the permittivityof the photocured composition can be 2 to 18, 2 to 14, or 2 to 12.Dielectric loss and relative permittivity can each be measured bysplit-post dielectric resonator testing at various frequencies, forexample 10 GHz, at a temperature of 23 to 25° C.

In a specific aspect, the photocurable compositions can include 35 to 85wt %, preferably 35 to 65 wt %, of the photoreactive oligomer component,which includes a urethane methacrylate-derivatized polybutadieneoligomer; 15 to 65 wt %, preferably 45 to 65 wt %, of the photoreactivemonomer component, which includes ethylene glycol dimethacrylate,trimethylolpropane trimethacrylate, and 2-ethylhexyl acrylate; and 0.1to 5 wt % of the photoinitiation composition, wherein each weightpercent is based on the total weight of the photoreactive oligomercomponent, the photoreactive monomer component, and the photoinitiatorcomposition, and totals 100 weight percent. The photocurable compositioncan include 10 to 40 wt % of the ethylene glycol dimethacrylate, 5 to 20wt % of the trimethylolpropane trimethacrylate, and 5 to 20 wt % of the2-ethylhexyl acrylate, based on the total weight of the photoreactiveoligomer component, the photoreactive monomer component, and thephotoinitiator composition, and totals 100 wt %. In this aspect, thephotocurable composition further includes 10 to 50 vol %, or 10 to 40vol % of a particulate filler, preferably which includes alumina andbarium nonatitanate, based on the total volume of the photocurablecomposition including the filler. The photocurable composition isSLS-printable as described below. The photocured material can have adielectric constant of 4.7 to 5.1 a dielectric loss of less than 0.004at 10 GHz.

A method for forming the photocurable composition includes combining thevarious components of the composition. The components can be added inany suitable order and in a suitable amount. The method of combining isnot specifically limited, and can comprise stirring, shaking, milling,or ultrasonic mixing. If transported or stored, the photocurablecomposition is preferably protected from light and or heat. Thephotocurable composition at a thickness of 0.020 inch (0.05 cm) can havea cure time of 6 to 30 seconds, or 10 to 25 seconds, or 15 seconds at22° C. under SLA manufacturing conditions as described below. “Curable”and “curing” as used herein includes polymerizable and crosslinkable,and polymerizing and crosslinking.

The photocurable composition is used for manufacture ofthree-dimensional polymer objects by SLA. In these methods, successivethin layers of a photopolymerizable composition are selectivelyphotopolymerized using a light source. This process has been described,for example, in U.S. Pat. Nos. 4,575,330, 4,929,402, 5,104,592,5,184,307, 5,192,559, 5,234,636, 5,236,637, and 5,273,691. In apreferred aspect, the method is a stereolithographic method asdescribed, for example, in U.S. Pat. No. 9,205,601.

Approaches to SLA include direct/laser writing and mask-based writingusing digital projection. In direct/laser writing a stage on which thepolymer material is formed is located just below a surface of a volumeof a curable liquid resin composition for the formation of a polymer. Asingle light source (e.g., a laser) moves along the surface of thecurable composition, row by row, until completely curing the desiredlayer. To initiate the following layer, the stage sinks lower into thevolume of the curable liquid resin composition until a new layer of thecurable composition covers the surface and the curing process repeats.In between layers, a blade loaded with the curable liquid resincomposition levels the surface of the resin to ensure a uniform layer ofliquid prior to another round of light exposure. This procedure repeatsuntil the curable liquid resin composition is printed to form the 3Dstructure.

In another approach, mask-based writing using digital projection, thestage is submerged a defined distance into the volume of the liquid,curable composition. The volume is located in a bath having an opticallyclear bottom. Next, the light source is guided to the stage in a patternto polymerize the curable composition between the light source and thestage. In the digital projection method, a digital mirror device allowsan entire layer of a given pattern to be cured simultaneously. The stagecan then be raised by a defined distance, and another layer can becured. This procedure repeats until the curable liquid resin compositionis printed to form the 3D structure.

After the component is manufactured, the 3D-printed component canoptionally be post-cured, e.g., further crosslinked. This can beaccomplished by further exposure to UV radiation. If a thermosettingresin composition is included in the photocurable composition, thepost-cure can be thermal, for example by exposure to heat in an oven.

The resulting polymeric structure can have any suitable configuration orshape. The resulting polymeric structure formed by SLA is a unified bodythat can be solid or porous. In an aspect, the body is porous, such thatair contributes to the overall dielectric constant of the body. Asdiscussed above, use of a higher dielectric constant filler allows themanufacture of such structures having the desired Dk. In addition, thedielectric loss can be very low, depending on the loss of the materialas well as the porosity of the material. For example, a polymericstructure can be have a dielectric loss factor of less than 0.01, orless than 0.008, or less than 0.006, or less than 0.004, or less than0.002, or less than 0.001, each measured at a frequency of 10 GHz. Forexample, the photocured polymer components can have a dielectric lossfactor of 0.0001 to 0.01, or 0.0001 to 0.008, or 0.0001 to 0.006, or eor 0.0001 to 0.004, or 0.0001 to 0.002, or 0.0001 to 0.001, eachmeasured at a frequency of 10 GHz.

In an aspect, the polymer structure is disposed on, or directly contactsan electrically conductive layer. In some aspects, at least twoalternating polymer structures or at least two alternating layers of theelectrically conductive layer are present to form a stack. Usefulelectrically conductive materials for the conductive layer include, forexample, stainless steel, copper, gold, silver, aluminum, zinc, tin,lead, a transition metal, or a combination thereof. There are noparticular limitations regarding the thickness of the conductive layer,nor are there any limitations as to the shape, size, or texture of thesurface of the electrically conductive layer. The conductive layer canhave a thickness of 1 to 2000 micrometers, or 10 to 1000 micrometers.When two or more conductive layers are present, the thickness of eachlayer can be the same or different. The conductive layer can comprise acopper layer. Suitable conductive layers include a thin layer of aconductive metal such as a copper foil presently used in the formationof circuits, for example, electrodeposited copper foils.

The conductive layer can be contacted with the polymer structure byplacing the conductive layer on the platform used for the additivemanufacturing process, and printing onto the conductive layer.Alternatively, the polymer material can be contacted with the conductivelayer by direct laser structuring, or by adhesion. Other methods knownin the art can be used to apply the conductive layer where permitted bythe particular materials and form of the polymer materials, for example,electrodeposition, chemical vapor deposition, and the like.

For example, the conductive layer can be applied by laser directstructuring. Here, the 3D-printed polymer material can comprise a laserdirect structuring additive, and the laser direct structuring cancomprise using a laser to irradiate the surface of the substrate,forming a track of the laser direct structuring additive, and applying aconductive metal to the track. The laser direct structuring additive cancomprise a metal oxide particle (such as titanium oxide and copperchromium oxide). The laser direct structuring additive can comprise aspinel-based inorganic metal oxide particle, such as spinel copper. Themetal oxide particle can be coated, for example, with a compositioncomprising tin and antimony (for example, 50 to 99 wt % of tin and 1 to50 wt % of antimony, based on the total weight of the coating). Thelaser direct structuring additive can comprise 2 to 20 parts of theadditive based on 100 parts of the respective composition. Theirradiating can be performed with a YAG laser having a wavelength of1,064 nanometers under an output power of 10 Watts, a frequency of 80kilohertz (kHz), and a rate of 3 meters per second. The conductive metalcan be applied using a plating process in an electroless plating bathcomprising, for example, copper.

The conductive layer can be adhesively contacted. In an aspect, thepolymer structure can first be formed by photopolymerization. When athermal cure agent is present in the polymer material composition, thepolymer structure and the electrically conductive layer can be contactedand adhered by thermal cure of the polymer material in the polymerstructure. This technique allows “B-staging” of the polymer structures.It is particularly useful where multilayer structures are desired. Forexample, a plurality of layers of the polymer structures can bemanufactured (B-staged); a stack of alternating polymer layers andconductive layers can be made; and then the stack can be thermally curedto adhere the layers. In other aspects, a polymer structure can bemanufactured (B-staged) in the form of a flat sheet; a conductive layercan be contacted with the flat sheet; the layers can be rolled toprovide a cylinder of alternating polymer sheet and conductive layer;and the roll can be thermally cured to adhere the layers.

Alternatively, or in addition, an adhesion layer can be disposed betweenone or more conductive layers and the polymer material.

Polymer structures useful at various radiofrequencies, including 3G, 4G,and 5G applications can be manufactured. The polymer structures can beused as or in an electronic device, for example as an impedance-matchinglayer, a dielectric waveguide, a lens, a reflect array, an antennamatching structure, a superstrate, a coupler, a divider, a radome, or adielectric antenna (including dielectric resonant antennas).

The compositions and methods described herein allow fast, efficientmanufacture of materials having very low loss, in a variety ofconfigurations and a variety of shapes, including geometrically complexparts. It also allows for the ability to create structures with agradient dielectric constant throughout all dimensions of a part, withone material and process. The compositions and methods have many otheradvantages, including dramatically reducing the time from design toprototyping to commercial product. Since no tooling is needed, designchanges can be made quickly. Minimal energy is used, compared toinjection molding or other molding processes. Use of additivemanufacturing can also decrease the amount of waste and raw materials.The compositions and methods can further reduce the parts inventory fora business since parts can be quickly made on-demand and on-site.

EXAMPLES

Materials

The materials shown in the below Table were used in the Examples.

Material CAS No. Trade Name, Source Isobornyl methacrylate    7534-94-3SR423A, Sartomer Isobornyl acrylate    5888-33-5 SR506C, SartomerEthylene glycol dimethacrylate      97-90-5 SR206, Sartomer1,6-Hexanediol diacrylate   13048-33-4 SR238B, SartomerTrimethylolpropane trimethacrylate    3290-92-4 SR351H, SartomerTrimethylolpropane triacrylate   15625-89-5 SR350, Sartomer1,6-Hexanediol dimethacrylate    6606-59-3 SR239, Sartomer 2-Ethylhexylmethacrylate     688-84-6 Norsocryl 2EHA, Arkema 2-Ethylhexyl acrylate    103-11-7 2-EHMA F, BASF 1,3 Butanediol dimethacrylate    1189-08-8SR214A, Sartomer Urethane methacrylate-derivatized   68987-46-2 TE-2000,Nippon polybutadiene oligomer Soda Co., Ltd (Mn = 2,500 g/mol) Urethanemethacrylate-derivatized 1345023-61-1 TEAI-1000, Nippon polybutadieneoligomer Soda Co., Ltd. (Mn = 2,400 g/mol) (1,3-Butadiene, homopolymer,hydrogenated, 2-hydroxyethyl-terminated,bis[N-[2-methyl-5-[[[2-[(1-oxo-2- propen-1-yl)oxy]ethoxy]carbonyl]amino]phenyl]carbamates])Test Methods

Viscosity was determined using a Brookfield viscometer at 23° C.

Dielectric loss (Df) and dielectric constant (Dk) were determined bysplit-post dielectric resonator (SPDR) testing. This method isdescribed, for example, in Krupka J., Gregory A. P., Rochard O. C.,Clarke R. N., Riddle B., Baker-Jarvis J., “Uncertainty of ComplexPermittivity Measurement by Split-Post Dielectric Resonator Techniques,”Journal of the European Ceramic Society, Number 10, pp. 2673-2676, 2001;and in Krupka, J., Geyer, R. G., Baker-Jarvis, J., Ceremuga, J.,“Measurements of the complex permittivity of microwave circuit boardsubstrates using split dielectric resonator and reentrant cavitytechniques”, Seventh International Conference on Dielectric Materials,Measurements and Applications, (Conf. Publ. No. 430), pp. 21-24,September 1996. Testing was conducted at a temperature of 23° C.

Example 1 Preparation of Polybutadiene Urethane Acrylate PhotocurableCompositions (Unfilled)

An array of photocurable compositions were prepared using urethanepolybutadiene methacrylate resin (TE-2000) as the photoreactive oligomerwith the photoreactive monomers isobornyl methacrylate, isobornylacrylate, ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate,trimethylolpropane trimethacrylate, trimethylolpropane triacrylate,1,6-hexanediol dimethacrylate, 2-ethylhexyl acrylate, 2-ethylhexylmethacrylate, hydroxypropyl methacrylate, and 1,3-butanedioldimethacrylate in amounts of 10 to 90 wt %, based on a total weight ofthe composition. Each composition also included 1 wt % of photoinitiatorBAPO (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), based on thetotal weight of the composition.

To prepare each composition, the oligomer was heated to 60° C. to reduceviscosity sufficiently to allow measuring and dispensing the material.The oligomer, monomers, and photoinitiator were mixed in a container viaa LabRam II acoustic mixer from Resodyn Acoustic Mixers for 5 minutes at50 g acceleration. The composition was allowed to cool to roomtemperature, and then coated into a thin film and exposed to UVradiation in a Dymax 5000-EC UV flood oven with a mercury bulb. Thesolid cured films were suitable to use in a split-post dielectricresonator test to measure dielectric constant and loss.

Viscosity, dielectric loss, cure time, and permittivity evaluation areprovided in Tables 1 to 5.

Table 1 illustrates the effect of different monomers on loss onphotocured polymers prepared using polybutadiene methacrylate resin(TE-2000) as the photoreactive oligomer and each listed monomer in anamount of 60 wt %, based on the total weight of the compositions.

TABLE 1 Methacryl/ Funct. Mol Mass, Df at Monomer Acryl No.* g/mol 10GHz Isobornyl methacrylate Methacryl 1 222.3 0.0088 Isobornyl acrylateAcryl 1 208.3 0.0118 Ethylene glycol dimethacrylate Methacryl 2 198.20.0069 1,6-Hexanediol diacrylate Acryl 2 226.3 0.0174 TrimethylolpropaneMethacryl 3 338.4 0.0079 trimethacrylate Trimethylolpropane triacrylateAcryl 3 296.3 0.0141 1,6-Hexanediol dimethacrylate Methacryl 2 254.30.0078 2-Ethylhexyl methacrylate Acryl 1 198.3 NS 2-Ethylhexyl acrylateAcryl 1 184.3 NS 1,3 Butanediol dimethacrylate Methacryl 2 226.3 NS*Number of (meth)acrylate groups NS-No sample could be made

As can be seen in Table 1, loss (Df) is generally higher when themonomer contained acrylate versus methacrylate groups. No trend wasobserved based on functionality of the monomer, or on molecular mass.

Table 2 shows the effect of amount and type of monomer on viscosity ofphotocurable polymer compositions prepared using polybutadienemethacrylate resin (TE-2000) as the photoreactive oligomer. The amountof each listed monomer is based on the total weight of the photocurablecompositions. In Table 2, “X” represents a composition having too high aviscosity to be SLA printable. A viscosity in the range of 1 to 250 cPis too liquid for efficient SLA printing. A viscosity in the range of250 to 10,000 cP is efficiently SLA-printable.

TABLE 2 Viscosity (Centipoise) Monomer, wt. % Monomer 10 20 30 40 50 6070 80 90 Isobornyl methacrylate X X X 14,000 1,900 575 300 75 50Isobornyl acrylate X X X 6,400 1,000 600 200 60 30 Ethylene glycoldimethacrylate X X 14,200 2,000 425 125 50 40 25 1,6-Hexanedioldiacrylate X X 16,800 2,700 800 250 150 60 40 Trimethylolpropane X X X X5,700 2,400 600 350 120 trimethacrylate Trimethylolpropane triacrylate XX X X 6,800 2,300 900 275 225 1,6-Hexanediol dimethacrylate X 12,4007,200 2,600 600 200 100 50 20 2-Ethylhexyl acrylate 12,800 4,800 2,400800 250 100 40 20 16 2-Ethylhexyl methacrylate 12,000 7,600 3,100 950350 100 40 20 16 Hydroxypropyl methacrylate X 21,600 12,800 1,500 950700 200 1,3-Butanediol dimethacrylate X X 4,800 1,200 500 250 100 30 10

As can be seen from Table 2, good viscosities with this composition(without filler) are generally attained when the monomer component ispresent in the range of 30 to 70 weight percent based on total weight ofmonomer and oligomer. Each preferred amount of monomer varies with eachmonomer, however.

Table 3 shows the effect of amount and type of monomer on dielectricloss (Df) of photocured polymers prepared using polybutadienemethacrylate resin (TE-2000) as the photoreactive oligomer. The amountof each listed monomer is based on the total weight of the photocurablecompositions. In Table 3, “X” represents a composition having too high aviscosity to be SLA printable, “˜” represents a composition that curestoo slowly for SLA printing (resulting in a polymer to “sticky” to beuseful as an electronic device), and “-” represents a composition havingtoo low a viscosity to be SLA printable.

TABLE 3 Dielectric Loss (Df) Monomer, wt. % Monomer 10 20 30 40 50 60 7080 90 Isobornyl methacrylate X X X X 0.0154 0.0088 0.0067 — — Isobornylacrylate X X X X 0.0119 0.0118 0.0073 — — Ethylene glycol dimethacrylateX X X 0.0072 0.0071 0.0069 — — — 1,6-Hexanediol diacrylate X X X 0.01590.0163 0.0174 — — — Trimethylolpropane X X X X X 0.0079 0.0122 — —trimethacrylate Trimethylolpropane triacrylate X X X X X 0.0141 0.0158 —— 1,6-Hexanediol dimethacrylate X X X ~ 0.0096 0.0078 — — — 2-Ethylhexylacrylate X X ~ ~ 0.0080 ~ — — — 2-Ethylhexyl methacrylate X X X ~ ~ ~ —— — Hydroxypropyl methacrylate X X X 0.0166 0.0234 0.0182 — — —1,3-Butanediol dimethacrylate X X X 0.0066 0.0060 ~ — — —

As shown in Table 3, the amount of each monomer that provides optimalviscosity and dielectric loss varies for each monomer.

Table 4 shows the effect of amount and type of monomer on cure time ofphotocurable compositions prepared using polybutadiene methacrylateresin (TE-2000) as the photoreactive oligomer. The amount of each listedmonomer is based on the total weight of the photocurable compositions.In Table 4, “X” represents a composition having too high a viscosity tobe SLA printable and “-” represents a composition having too low aviscosity to be SLA printable.

TABLE 4 Cure time (seconds) Monomer (wt %) Monomer 10 20 30 40 50 60 7080 90 Isobornyl methacrylate X X X X 30* 9 15 — — Isobornyl acrylate X XX X 15 — — Ethylene glycol dimethacrylate X X X 12  12  15  — — —1,6-Hexanediol diacrylate X X X 9 — — — Trimethylolpropane X X X X X 9 —— trimethacrylate Trimethylolpropane triacrylate X X X X X 15   6 — —1,6-Hexanediol dimethacrylate X X X 15  9 6 — — — 2-Ethylhexyl acrylateX X 25* 25* 9 25* — — — 2-Ethylhexyl methacrylate X X X 30* 30* 30* — —— Hydroxypropyl methacrylate X X X 9 15  18* — — — *Composition curestoo slowly for SLA printing, resulting in a “sticky” polymer not usefulas an electronic device.

As shown in Table 4, the amount of each monomer that provides optimalviscosity and cure time varies for each monomer.

Table 5 shows the effect of amount and type of monomer on the dielectricconstant of photocured polymers prepared using polybutadienemethacrylate resin (TE-2000) as the photoreactive oligomer. The amountof each listed monomer is based on the total weight of the photocurablecompositions. In Table 4, “X” represents a composition having too high aviscosity to be SLA printable and “-” represents a composition havingtoo low a viscosity to be SLA printable.

TABLE 5 Dielectric constant Monomer, wt. % Monomer 10 20 30 40 50 60 7080 90 Isobornyl methacrylate X X X X 2.0882 2.4512 2.3860 — — Isobornylacrylate X X X X 2.1668 2.3858 2.4634 — — Ethylene glycol dimethacrylateX X X X 2.7825 2.1551 — — — 1,6-Hexanediol diacrylate X X X X 2.43952.3719 — — — Trimethylolpropane X X X X X 2.2263 2.2270 — —trimethacrylate Trimethylolpropane triacrylate X X X X X 2.5459 2.6927 —— 1,6-Hexanediol dimethacrylate X X X ~ 2.2329 2.4382 — — — 2-Ethylhexylacrylate X X ~ ~ 2.3336 ~ — — — 2-Ethylhexyl methacrylate X X X ~ ~ ~ —— — Hydroxypropyl methacrylate X X X 2.3058 2.2916 2.2217 — — —1,3-Butanediol dimethacrylate X X X 2.0771 2.0574 ~ — — —

As shown in Table 5, with no filler present, SLA-printable compositionscan be obtained having a dielectric constant in the range of 2.0771 to2.7825.

Example 2

A composition including 60 wt % TE-2000 oligomer, 20 wt % 2-ethylhexylacrylate, and 20 wt % ethylene glycol dimethacrylate was prepared with 1part per hundred (pph) of BAPO photoinitiator added. Without filler thematerial had a viscosity of 500 centipoise at 23° C. by Brookfieldviscometer, a dielectric constant of 2.3 and dielectric loss of 0.0064at 10 GHz.

A formulation with silica filler was also prepared by further additionof 30 vol % of silica (FB-8S from Denka) treated with approximately 1 wt% methacryloxypropyltrimethoxysilane and subsequently mixing in a LabRamII acoustic mixing system for 5 minutes at 50 g acceleration. Thesilica-filled composition measured a viscosity of 3,000 cP at 23° C. viaa Brookfield viscometer, and was cured with exposure to UV radiation ina Dymax 5000-EC UV flood oven with a mercury bulb. The solid cured filmswere suitable to use in a split-post dielectric resonator test tomeasure dielectric constant and loss. The material measured a dielectricconstant of 2.5 and loss of 0.0046 at 10 GHz.

A formulation with alumina filler was also prepared by addition of 30vol % of alumina (DAW-10 from Denka) treated with approximately 1 wt %methacryloxypropyltrimethoxysilane. The alumina filled composition had aviscosity of 4500 centipoise at 23° C. by Brookfield viscometer, adielectric constant of 3.4, and dielectric loss of 0.0041 at 10 GHz.

Example 3

A composition including 40 wt % of a urethane methacrylate polybutadieneoligomer (TEAI-1000), 30 wt % isobornyl methacrylate, 20 wt % ethyleneglycol dimethacrylate, and 10 percent trimethylolpropane trimethacrylatewas prepared with 1 part per hundred by weight (pph) of BAPOphotoinitiator and 0.1 pph of scintillating agent2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene added. Subsequently, 18vol % of alumina (DAW-10 from Denka) treated with approximately 1 wt %methacryloxypropyltrimethoxysilane, and 19 vol % of barium nonatitanate(Trans-Tech) treated with approximately 1 wt % of oleyl titanate wasadded to the composition, each based on the total volume of thecomposition. The resulting photocured material had a dielectric constantof 4.9 and loss of 0.0035 at 10 GHz.

Example 4

A composition including 60 wt % of a urethane methacrylate polybutadieneoligomer (TEAI-1000), 15 wt % isobornyl methacrylate, 10 wt % ethyleneglycol dimethacrylate, 10 wt % trimethylolpropane trimethacrylate, and 5wt % 2-ethylhexyl acrylate was prepared with 1 pph of BAPOphotoinitiator and 0.1 pph of scintillating agent2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene added. Subsequently, 18vol % of alumina (DAW-10 from Denka) treated with approximately 1 wt %methacryloxypropyltrimethoxysilane, and 19 vol % of barium nonatitanate(Trans-Tech) treated with approximately 1 wt % of oleyl titanate wereadded to the composition, each based on the total volume of thecomposition. The resulting photocured material measured a dielectricconstant of 4.9 and loss of 0.0039 at 10 GHz.

Example 5

Six samples A-F were formulated using a 50 wt % mixture of a urethaneacrylic polybutadiene oligomer (TEAI-1000) with 50 wt % of a monomercomponent, then 1 wt %, based on the total weight of the oligomer andmonomer BAPO photoinitiator was added. In Sample A, the monomercomponent is 100% trimethylolpropane trimethacrylate. The amount insubsequent Samples B-E decreases in 20 wt % increments, being replacedby trimethylolpropane triacrylate, until in Sample F where the monomercomponent is 100 wt % trimethylolpropane triacrylate. Dielectricconstant and dielectric loss were tested for each sample at 5 and 10GHz, and average results are shown in Table 6.

TABLE 6 Monomer component, wt % 5 GHz SPDR 10 GHz SPDR SampleMethacrylate Acrylate Avg Dk Avg DF Avg Dk Avg DF A 100 0 2.42 0.00502.57 0.0041 B 80 20 2.41 0.0051 2.38 0.0043 C 60 40 2.44 0.0060 2.440.0048 D 40 60 2.60 0.0073 2.46 0.0056 E 20 80 2.41 0.0062 2.55 0.0051 F0 100 2.33 0.0074 2.49 0.0059

The data in Table 6 shows that an increase in acrylate content versusmethacrylate content in the monomer component results in an increase indielectric loss.

Set forth below are various non-limiting aspects of the disclosure.

Aspect 1. A photocurable composition for stereolithographicthree-dimensional printing, wherein the photocurable compositioncomprises a photoreactive oligomer component comprising a hydrophobicoligomer comprising a photoreactive end group, a photoreactive monomercomponent comprising a photoreactive monomer having a photoreactive endgroup, and a photoinitiation composition comprising a photoinitiator;the photocurable composition has a viscosity of 250 to 10,000 centipoiseat 22° C., determined using a Brookfield viscometer; and the photocuredcomposition has a dielectric loss of less than 0.010, preferably lessthan 0.008, more preferably less than 0.006, most preferably less than0.004, each determined by split-post dielectric resonator testing at 10gigahertz at 23° C.

Aspect 2. The photocurable composition of Aspect 1, comprising 35 to 85wt % of the photoreactive oligomer component, 15 to 65 wt % of thephotoreactive monomer component, and 0.01 to 15 wt % of thephotoinitiation composition, wherein each weight percent is based on thetotal weight of the photoreactive oligomer component, the photoreactivemonomer component, and the photoinitiation composition, and totals 100weight percent

Aspect 3. The photocurable composition of Aspect 1 or Aspect 2, whereinthe hydrophobic oligomer comprises a (meth)acrylate end group,preferably two or more methacrylate end groups.

Aspect 4. The photocurable composition of any one of Aspects 1 to 3,wherein the hydrophobic oligomer of photoreactive oligomer component isa (meth)acrylate-derivatized polyester, a (meth)acrylate-derivatizedpolyurethane, a (meth)acrylate urethane-derivatized polybutadieneoligomer, or a combination thereof.

Aspect 5. The photocurable composition of any one of Aspects 1 to 4,wherein the photoreactive oligomer component comprises a urethane(meth)acrylate-derivatized polybutadiene oligomer having a numberaverage molecular weight of 500 to 5,000 g/mol.

Aspect 6. The photocurable composition of any one of Aspects 1 to 5,wherein the photoreactive monomer comprises a (meth)acrylate end group,preferably two or more methacrylate end groups.

Aspect 7. The photocurable composition of Aspect 6, wherein thephotoreactive monomer component comprises at least 50% by weight,preferably at least 60% by weight, more preferably at least 70% byweight of a methacrylate-functional monomer.

Aspect 8. The photocurable composition of Aspect 6, wherein a monomerhaving an acrylate end group is present in an amount of 20 wt % or less,based on the total weight of the photoreactive oligomer component andthe photoreactive monomer component.

Aspect 9. The photocurable composition of Aspect 7, wherein thephotoreactive monomer component comprises a combination of ethyleneglycol dimethacrylate, trimethylol propane trimethacrylate, andisobornyl methacrylate.

Aspect 10. The photocurable composition of any of Aspects 1 to 9,further comprising a particulate filler, in an amount of 5 to 60 vol %,preferably 10 to 60 vol %, more preferably 10 to 50 vol %, each based onthe total volume of the photocurable composition.

Aspect 11. The photocurable composition of Aspect 10, wherein theparticulate filler comprises silica, alumina, calcium titanate,strontium titanate, barium titanate, barium nonatitanate, boron nitride,aluminum nitride, or a combination thereof, preferably wherein theparticulate filler or combination thereof has a dielectric constant of 5or greater, more preferably wherein the particulate filler comprisesalumina, barium nonatitanate, or combination thereof.

Aspect 12. The photocurable composition of any of Aspects 1 to 11,wherein the photoinitiation composition further comprises an ultravioletlight-absorbing agent, preferably in an amount of 0.01 to 10 wt %, basedon the total weight of the photoreactive oligomer component, thephotoreactive monomer component, and the photoinitiation composition andtotals 100 weight percent.

Aspect 13. The photocurable composition of any of Aspects 1 to 12,wherein the photoinitiation composition further comprises scintillatingagent, preferably in an amount of 0.01 to 2 wt %, based on the totalweight of the photoreactive oligomer component, the photoreactivemonomer component, and the photoinitiation composition and totals 100weight percent.

Aspect 14. The photocurable composition of any one or more of Aspects 1to 13, having a relative permittivity of 2 to 12 at 10 gigahertz.

Aspect 15 A three-dimensional structure comprising a photocured productof the composition of any one of Aspects 1 to 14.

Aspect 16. The photocurable composition of any of Aspects 1 to 13,having a dielectric loss of less than 0.004 at 10 GHz as determined bysplit-post dielectric resonator testing at 10 GHz at a temperature of23° C.

Aspect 17. The three-dimensional structure of Aspect 15 or 16, whereinthe structure is porous.

Aspect 18. An electronic device comprising the three-dimensionalstructure of any one of Aspects 15 to Aspect 17.

Aspect 19. The electronic device of Aspect 18, wherein the device is animpedance-matching layer, a dielectric waveguide, a lens, a reflectivearray, an antenna matching structure, a superstrate, a coupler, adivider, a radome, or a dielectric antenna.

Aspect 20. The electronic device of Aspect 19, wherein at least oneelectrical conductor is disposed on or in contact with the photocuredproduct.

Aspect 21. A method of forming the photocurable composition of any oneor more of Aspects 1 to 15, the method comprising combining thecomponents of the composition.

Aspect 22. A stereolithographic method of manufacture of athree-dimensional polymer structure, the method comprising: providing avolume comprising the photocurable composition of any one or more ofAspects 1 to 15; irradiating a portion of the composition withactivating radiation in a pattern to form a photocured layer of thestructure; contacting the layer with the photocurable composition;irradiating the photocurable composition with activating radiation in apattern to form a second photocured layer on the first layer; andrepeating the contacting and irradiating to form the three-dimensionalpolymer structure.

Aspect 23. The method of Aspect 22, further comprising thermally curingthe three-dimensional structure.

Aspect 24. A three-dimensional structure made by the method of Aspect 22or Aspect 23, wherein the structure is porous.

Aspect 25. An electronic device comprising the three-dimensionalstructure of any one of Aspects 22 to 24.

Aspect 26. The electronic device of Aspect 23, wherein the device is animpedance-matching layer, a dielectric waveguide, a lens, a reflectivearray, an antenna matching structure, a superstrate, a coupler, adivider, a radome, or a dielectric antenna.

The compositions, methods, and articles can alternatively comprise,consist of, or consist essentially of, any appropriate materials, steps,or components herein disclosed. The compositions, methods, and articlescan additionally, or alternatively, be formulated so as to be devoid, orsubstantially free, of any materials (or species), steps, or components,that are otherwise not necessary to the achievement of the function orobjectives of the compositions, methods, and articles.

The terms “a” and “an” do not denote a limitation of quantity, butrather denote the presence of at least one of the referenced item. Theterm “or” means “and/or” unless clearly indicated otherwise by context.Reference throughout the specification to “an aspect,” “another aspect,”and “some aspects,” means that a particular element (e.g., feature,structure, step, or characteristic) described in connection with theaspect is included in at least one aspect described herein and may ormay not be present in other aspects. In addition, it is to be understoodthat the described elements can be combined in any suitable manner inthe various aspects. The term “combination” is inclusive of blends,mixtures, alloys, reaction products, and the like. “At least one of”means that the list is inclusive of each element individually, as wellas combinations of two or more elements of the list, and combinations ofat least one element of the list with like elements not named.Similarly, “a combination thereof” is open, and can include at least oneof the named elements, optionally together with a like or equivalentelement not named.

The endpoints of all ranges directed to the same component or propertyare inclusive of the endpoints, are independently combinable, andinclude all intermediate points and ranges. For example, ranges of “upto 25 wt %, or 5 to 20 wt %” is inclusive of the endpoints and allintermediate values of the ranges of “5 to 25 wt %,” such as 10 to 23 wt%, and the like.

When an element such as a layer, film, region, or substrate is referredto “contacting” or as being “on” another element, it can be directlycontacting or directly on the other element or intervening elements canalso be present. In contrast, when an element is referred to as“directly contacting” or as being “directly on” another element, thereare no intervening elements present.

Unless specified to the contrary herein, all test standards are the mostrecent standard in effect as of the filing date of this application, or,if priority is claimed, the filing date of the earliest priorityapplication in which the test standard appears.

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as is commonly understood by one of skill in theart to which this invention belongs. All cited patents, patentapplications, and other references are incorporated herein by referencein their entirety. However, if a term in the present applicationcontradicts or conflicts with a term in the incorporated reference, theterm from the present application takes precedence over the conflictingterm from the incorporated reference.

While particular embodiments have been described, alternatives,modifications, variations, improvements, and substantial equivalentsthat are or can be presently unforeseen can arise to applicants orothers skilled in the art. Accordingly, the appended claims as filed andas they can be amended are intended to embrace all such alternatives,modifications variations, improvements, and substantial equivalents.

What is claimed is:
 1. A photocurable composition for stereolithographicthree-dimensional printing, wherein the photocurable compositioncomprises a photoreactive oligomer component comprising a hydrophobicoligomer comprising a photoreactive end group, a photoreactive monomercomponent comprising a photoreactive monomer having a photoreactive endgroup, wherein the photoreactive monomer component comprises at least50% by weight of a methacrylate-functional monomer, and aphotoinitiation composition comprising a photoinitiator; thephotocurable composition has a viscosity of 250 to 10,000 centipoise at22° C., determined using a Brookfield viscometer; and the photocuredcomposition has a dielectric loss of less than 0.010 determined bysplit-post dielectric resonator testing at 10 gigahertz at 23° C.
 2. Thephotocurable composition of claim 1, comprising 35 to 85 weight percentof the photoreactive oligomer component, 15 to 65 weight percent of thephotoreactive monomer component, and 0.01 to 15 weight percent of thephotoinitiation composition, wherein each weight percent is based on thetotal weight of the photoreactive oligomer component, the photoreactivemonomer component, and the photoinitiation composition, and totals 100weight percent.
 3. The photocurable composition of claim 1, wherein thehydrophobic oligomer of the photoreactive oligomer component comprises a(meth)acrylate end group.
 4. The photocurable composition of claim 1,wherein the hydrophobic oligomer of the photoreactive oligomer componentis a (meth)acrylate-derivatized polyester, a (meth)acrylateurethane-derivatized polybutadiene oligomer, or a combination thereof.5. The photocurable composition of claim 1, wherein the hydrophobicoligomer of the photoreactive oligomer component comprises a urethane(meth)acrylate-derivatized polybutadiene oligomer having a numberaverage molecular weight of 500 to 5,000 grams per mole.
 6. Thephotocurable composition of claim 1, wherein the photoreactive monomercomprises a methacrylate end group.
 7. The photocurable composition ofclaim 6, wherein a monomer having an acrylate end group is present in anamount of 20 weight percent or less, based on the total weight of thephotoreactive oligomer component and the photoreactive monomercomponent.
 8. The photocurable composition of claim 7, wherein thephotoreactive monomer component comprises a combination of ethyleneglycol dimethacrylate, trimethylol propane trimethacrylate, andisobornyl methacrylate.
 9. The photocurable composition of claim 1,further comprising a particulate filler in an amount of 5 to 60 vol %based on the total volume of the photocurable composition.
 10. Thephotocurable composition of claim 9, wherein the particulate fillercomprises silica, alumina, calcium titanate, strontium titanate, bariumtitanate, barium nonatitanate, boron nitride, aluminum nitride, or acombination thereof.
 11. The photocurable composition of claim 1,wherein the photoinitiation composition further comprises an ultravioletlight-absorbing agent in an amount of 0.01 to 10 weight percent, basedon the total weight of the photoreactive oligomer component, thephotoreactive monomer component, and the photoinitiation composition,which totals 100 weight percent.
 12. The photocurable composition ofclaim 1, wherein the photoinitiation composition further comprisesscintillating agent in an amount of 0.01 to 2 weight percent, based onthe total weight of the photoreactive oligomer component, thephotoreactive monomer component, and the photoinitiation composition andtotals 100 weight percent.
 13. The photocurable composition of claim 1,having a relative permittivity of 2 to 12 at 10 gigahertz.
 14. Athree-dimensional structure comprising a photocured product of thecomposition of claim
 1. 15. The three-dimensional structure of claim 14,having a dielectric loss of less than 0.004 at 10 GHz as determined bysplit-post dielectric resonator testing at 10 gigahertz at a temperatureof 23° C.
 16. The three-dimensional structure of claim 14, wherein thestructure is porous.
 17. An electronic device comprising thethree-dimensional structure of claim
 14. 18. The electronic device ofclaim 17, wherein the device is an impedance-matching layer, adielectric waveguide, a lens, a reflective array, an antenna matchingstructure, a superstrate, a coupler, a divider, a radome, or adielectric antenna, wherein at least one electrical conductor isdisposed on or in contact with the photocured product.
 19. Astereolithographic method of manufacture of a three-dimensional polymerstructure, the method comprising: providing a volume comprising thephotocurable composition of claim 1; irradiating a portion of thecomposition with activating radiation in a pattern to form a photocuredlayer of the structure; contacting the layer with the photocurablecomposition; irradiating the photocurable composition with activatingradiation in a pattern to form a second photocured layer on the firstlayer; and repeating the contacting and irradiating to form thethree-dimensional polymer structure.
 20. The method of claim 19, furthercomprising thermally curing the three-dimensional structure.
 21. Athree-dimensional structure made by the method of claim 19 wherein thestructure is porous.
 22. An electronic device comprising thethree-dimensional structure of claim 21, wherein the device is animpedance-matching layer, a dielectric waveguide, a lens, a reflectivearray, an antenna matching structure, a superstrate, a coupler, adivider, a radome, or a dielectric antenna.
 23. The photocurablecomposition of claim 1, having a dielectric loss of less than 0.004. 24.The photocurable composition of claim 3, wherein the hydrophobicoligomer of the photoreactive oligomer component comprises two or moremethacrylate end groups.
 25. The photocurable composition of claim 6,wherein the photoreactive monomer comprises two or more methacrylate endgroups.
 26. The photocurable composition of claim 9, comprising theparticulate filler in an amount of 10 to 50 vol %, based on the totalvolume of the photocurable composition.
 27. The photocurable compositionof claim 10, wherein the particulate filler comprises alumina, bariumnonatitanate, or combination thereof.
 28. The photocurable compositionof claim 1, wherein the photoreactive monomer component comprises atleast 60% by weight of the methacrylate-functional monomer.
 29. Thephotocurable composition of claim 1, wherein the photoreactive monomercomponent comprises at least 70% by weight of themethacrylate-functional monomer.